Process for producing synthetic lumber that is not attacked by insects



Patented Nov. 28, 1933 PROCESS FOR PRODUCING SYNTHETIC LUMBER THAT IS INSECTS NOT ATTACKED BY I Orland R. Sweeney, Ames, Iowa, assignor to Iowa State College of Agriculture and Mechanical granted Ma 5, 1931.

Arts, Ames, Iowa, a corporation of Iowa llo Drawing. Original application June 27, 1929, Serial No. 374,274,- now Patent No. 1,803,737,

Divided and this application February 9, 1931. Serial No. 514,705

Claims.

This invention relates tothe process or method of treating synthetic lumber, paper or the like against attacks from insects. illustration I will specifically consider and here- 5 in discuss the treating of synthetic lumber made from cornstalks against such attacks by ants and the like. To this end the invention may consist of, first; cooking the unshredded corn plant under pressure, second; allowing it to stand for a certain length of time without washing it, third; passing it througha rod mill or like,- fourth; suitably washing the same, fifth; passing the washed product through a refining machine, sixth; treating said material with a suitable amount of water, seventh; adding to said mass a sizing material such as rosin or alum, eighth; mixing corrosive sublimate in the mass, and ninth; forming it into a board and drying it on a suitable machine. When such a board is formed it will be economical in manufacture, durable and strong in use, and will be free from the possibility of its deterioration by insects either "boring or nesting inside the board or eating it. The

step by step procedure may be varied as will hereinafter be explained. Heretofore, a great deal of experimenting has been done in attempting to make suitable syntheticlumber from cornstalks and from this standpoint I might state that my application for United States Letters Patent on a process relating to the production of synthetic lumber from cornstalks, Serial No. 374,274, filed June 27, 1929 now Patent No. 1,803,737, date May 5, 1931, and of which this invention is a division, goes into great detail to explain. 1

Sufiice it to say that the examination of the cornstalk shows that it is composed of a hard outer shell called the cortex. This cortex surrounds a soft pulpy material known as pith or parenchyma, and this pith surrounds elongated cell fibers called vascular bundles. Any processing of this material is diflicult because of the different physical properties. For example, if the grinding machinery is not especially adapted to the purpose, the pith will be beat to a jelly long before pieces of the outside fibers are reduced to a suitable pulp.

This causes the mat forming machine to become clogged and produce an unsatisfactory product. Likewise in the digesting of the cornstalks with chemicals, no wholly satisfactory process has been worked out because the pith and vascular bundles are completely hydrolyzed and disintegrated'before the cortex is properly cooked. In the standard practice it is the custom to For purposes of shred or otherwise comminute the comstalks before subjecting them to cooking or chemical treatment.

I have found that if the cornstalks be unshredded and then fed into the digester as they come in bales or directly from the field, before they have been given any serious mutilation, and that if the digestion be carried out using approximately pure water, or in other words water whose pH value does not vary greatly from 7.0, and that if these whole unmutilated stalks are subjected to a pressure of from thirty to one hundred pounds in contact with hot water, that there results a product which when properly macerated gives a board of great strength and of highly desirable properties for use in the arts.

I have also found that it is advisable after cooking the comstalks for from one to three hours under such a pressure with hot water, that the fibers will be made tougher and that the pith cells will draw into fiber better and be removed more completely from the fibrous cortex cells it I allow the cooked stalks to stand for from four to twenty-four hours before they are further han dled in the processes. This standing has a double advantage in that it allows the fibers to absorb from the cook liquors ligneous or pentosic materials which probably partly oxidize and at the same time the greater amount of the cooking liquors drain away thus reducing the necessity for excessive washing of the material.

In order to get the best results from the water digested fibers or cornstalks as prepared in the foregoing manner, I next pass the cornstalksthrough a heavy rod mill. This rod mill is of the usual construction consisting of a large drum mounted for rotation and having a plurality of heavy rods therein. i

As the drum revolves on its axis the rods naturally either tumble over each other or rise upon the side of the drum and slide down continuously. It is obvious that if the rods tumble from the top portion of the drum downwardly, a pounding action will result, whereas if the rods slide down the side they will give a rubbing action to the material inside the drum.

For my purposes I prefer the rubbing action as it draws the pith cells into long fibers which do not jell up and which work better when commingled with the tough, strong cortex fibers. The obtaining of this result will vary with the different types of rod mills, but any skilled workman can easily determine the. speed the drum should rotate for realizing this rubbing action. Results Will also depend on the rate the cornstalks are fed into the mill. Obviously the largerthe rods and rod mill the greater the feed must be in order to produce satisfactory fiber.

I have found that it is best to run the cornstalks through at such a rate as to cause the cortex fibers at the discharge end to vary in lengths from very short fibers to fibers of about one-half inch in length. Best results are not generally obtained by attempting to completely reduce the cent of the Weight of the cornstalks fed into the.

mill.

After the pulp has come through the mill it is now coarse enough to be free on a screen which is so positioned as to receive the pulp. It is upon this screen that the cornstalk pulp is washed with water to remove a certain amount of the pentosans and lignins produced during the water cooking. This washing must not be too thorough because the adhesive properties of these beforementioned materials are desirable. If, however, none of the lignins or pentosans are washed out, the board will not be free enough on the -machines used to make up the same. Thescreen should be of approximately forty mesh and may be either of the inclined sheet type or the rotating cylinder type. As the pulp travels down and across the screen it is washed by the water sprayed on it which can be controlled by a valve in the water line.

If a very refined board is desired, the pulp from the washing screen should be passed through a refiner in order to take out the small pieces of material which are sometimes termed shiners or chives. After thepulp is Washed, a suitable amount of water is added to the same and to this mass usually is added a sizing material such as rosin or alum. The mass is then conveyed to the board forming machine as is well known in the art.

The above discussion will give a general idea of one way of making and forming 'a synthetic lumber and will form a basis upon which I may discuss the treating of the same against insects. Therefore, generally I would state that this invention consists of injecting a substance into the pulped mass that is very poisonous to the insects.

Corrosive sublimate is' an excellent poison and may be successfully used by adding to the pulp suspension a few hundreds of a percent of the same, which is absorbed by the fibers. method of treating the syntheticlumber, the corrosive sublimate is thoroughly distributed throughout the board, thereby making it impossible for insects to attack the board either from the outside or inside. The habit of many insects such as termites or white ants is to bore into a board-at the end and penetrate the interior of the board without affecting the surface of the board, and after a certain length of time the board so attacked will be little more than a shell and unable to perform functions required of strong substantial boards. It is for this reason that ordinary board is so hard t0 t a g n By this ants as the poison placed on the board only penetrates the surface of the board and d0es.not ex-.

tend completely through the board, thereby making it possible for the ants to attack the inside of the lumber without harm to themselves. How ever, synthetic lumber as I herein describe provides a situation where the pulp can be treated by a corrosive sublimate and the ant repellent will therefore be completely throughout the syn thetic board.

When the pulp is placed on the board forming machine it is pressed in the usual manner by rollers or the like and the water removed from the same. The water thus removed is generally called white waters and I have found that for economy of water consumption it is desirable to use this water by returning it to the process. I use it direct for washing the pulp and for diluting the pulp in the refining machine.

In the process where the white Waters are used over again it is feasible and practical to continuously feed in the corrosive sublimate, and since the white waters, which contain the excess corrosive sublimate, are returned to the process there will be no loss of these materials except as they are absorbed in the board. By such a process as I have explained, i. e., the mixing of a small percent of corrosive sublimate in the pulp mass, the finished board will be effectively saturated with the corrosive sublimate.

After the corrosive sublimate is successfully mixed with the pulp mass it is passed to the usual board forming machine which largely removes the Water from the pulp and this pulp which is in the form of a damp mat is passed into a dryer and dried into the desired lumber.

I claim as my invention:

1. The. process of manufacturing and producing lumber'from cornstalks consisting in breaking up of the cornstalks in particles, injecting into the resultant mass a corrosive sublimate, and forming the mass into lumber by means of a suitable machine.

2. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the breaking up of the cornstalks into particles, washing the particles, treating the mass with corrosive sublimate, and lastly forming the mass 'into said lumber by means of a suitable pressing and drying machine.

' 3. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the breaking up of the cornstalks into comparatively fine pieces, washing the pieces,

commingling the pieces with water, treating the mass with corrosive sublimate, and then forming the mass into lumber by pressing and drying.

4. The process of manufacturing and producing a synthetic lumber from corn plant material consisting in the cooking of the unshredded plant in water, disintegrating the material by a suitable machine, commingling-the pieces with water, injecting corrosive sublimate into the disintegrated mass, and last forming the mass into lumber by pressing and drying.

5. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the cooking of the unshredded cornstalks in water under pressure, discharging the material from the cooker, breaking the material into particles by a suitable machine, adding water to the particles, injecting corrosive sublimate into the mass, and last forming the mass into lumber by pressing and drying.

6. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the cooking of the unshredded cornstalks at a pressure thirty pounds in water, discharging the material from the cooker, breaking tht material into particles by a suitable machine, adding water to the particles, injecting corrosive sublimate into the mass, and last forming the mass into lumber by pressing and drying.

'7. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the cooking of the unshredded corn plant in water under pressure, discharging the material from the cooker, rubbing and breaking the cornstalks into elongated particles by'a suitable machine such as a rod mill, treating the particles with water, injecting corrosive sublimateinto the mass, and last forming the mass into lumber by pressing and drying.

8. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the cooking of the cornstalks in water, breaking of the cornstalk material into particles, washing the particles, commingling the particles with water, treating the mass with a sizing ma.- terial, adding to the mass a corrosive sublimate, forming said mass into a mat on a forming machine, returning the white waters obtained-from the forming of the mat back into the process for diluting additional plant material coming through the process, and last forming the mass into lumber by pressing and 9. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the breaking of the cornstalk material into ing a synthetic lumber from corn plants consisting in the breaking up of the plants into comparatively small pieces, the adding of liquid to the pieces to form a mass, the treatingof the mass with an insecticide, and then forming themass into lumber by pressing and drying.

ORLAND R. SWEENEY. 

